Articulated die



Jan. 13, 1959 E. E. JONES ARTICULATED DIE Filed 001;. 22, 1954 5 Sheets-Sheet 1 FIGJ.

INVENTQR EVERETT E. JONES FIGS."

H IS ATTORNEYS 5 Sheets-Sheet 3 Filed Oct. 22, 1954 Q E F FIGS.

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IIOI Hls ATTORNEYS 1 Jan. 13, 1959 E. E. JONES ARTICULATED DIE 5 Sheets-Sheet 5 Filed Oct; 22, 1954 INVENTOR EVERETT E. JONES ARTICULAQTED DIE Everett E. Jones, Hagerstown, Md, assignor to Fairchild Engine and Airplane Corporation, Hagerstown, Md, a corporation of Maryland Application October 22, 1954, Serial No. 463,881 6 Claims. (Cl. 153--51) This invention relates to metal-forming methods and apparatus, and more particularly to a method and apparatus for forming relatively ductile metal parts, wherein the metal is brought into pressure contact with a flexible die, thereby causing the metal part to assume the shape or contour of the die.

One of the major costs in forming metal parts is incurred in the manufacture of the die, especially where the portion or edge of the part which is urged into pressure contact with the die has an unusual shape or contour, which shape or contour must be produced in matrix form in the surface of the die. It is evident that in such cases the die must be machined with great accuracy and care in order that the parts, after forming, will have the required dimensions, configuration, etc. This die cost is, of course, greatly multiplied where it is necessary to impart a different curvature to a plurality of parts of the same stock. Examples of such parts are the cap strips for built-up ribs of a tapered wing, longitudinal stiffeners for engine cowls, fuselage stiifeners, etc., and in each of these cases a separate die must be manufactured for each piece of different curvature.

The present invention has for its object, a method and apparatus wherein flexible dies are employed in the forming process, the flexible dies being composed of a plurality of articulated segments so that they can be formed to assume different bends, bows or curvatures. In this way all parts of the same stock can be formed with the same die, regardless of the curvature which is to be imparted thereto.

According to the present invention, the desired curvature is imparted to the flexible die by a flat templet, at least one edge of which is provided with the re quired curvature of the part to be formed. When the die is placed in operative relationship with the templet, the die assumes the curvature thereof, and the templet serves to maintain the flexible die rigid in the assumed shape during the forming operation. Thereafter, of course, if it is desired to produce a similar part of a different bend or curvature, it is necessary merely to replace the templet with one having a curved edge corresponding to the new part to be formed.

The present invention has a wide application to both stretch forming methods and press forming methods, and for a complete understanding thereof reference may be had to the detailed description which follows and the accompanying drawings in which:

Fig. 1 is an illustrative top-plan view showing the application of the present invention to a stretch forming operation;

Fig. 2 is a transverse cross-section view of the flexible die shown in Fig. 1;

Fig. 3 is a perspective exploded view of the' flexible die;

Figs. 4 to 8 are cross-section views illustrating the manner in which the present invention can be employed for l illnit ed b tates Patent "ice :5 forming parts of difierent cross-section by stretch forming methods;

Fig. 9 is a side elevation, partly in cross-section, of a clamping device suitable for anchoring the flexible die to a base during a stretch forming operation;

Fig. 10 is a cross-section View taken on the line 10- lti of Fig. 9;

Fig. 11 is a cross-section elevation view illustrating the application of the present invention to a press forming operation;

Fig. 12 is an isometric view of the lower flexible die shown in Fig. 11;

Fig. 13 is an isometric view of the upper flexible die shown in Fig. 11; and

Figs. 14 and 15 are isometric views of a modified form of lower die for the press shown in Fig. 11, the die in Fig. 14 being shown as an exploded. view.

Referring to Fig. 3 of the drawings, one form of the flexible die is shown comprising a plurality of segments 24 joined together by a flexible connection, such as the link chain 25 The front die faces 26 of the segments 24 are machined to the proper matrix contour of the part to be formed. The flexible die construction shown in Figs. 2 and 3 is adapted to be employed for forming parts of V-shaped cross-section, such as the part A shown in Pig. 2. Claw-like or hook-like registering members 21 are mounted to the upper surfaces of the segments 24, and in the particular embodiment shown in Figs. 2 and 3, the claw-like registering members are disposed forwardly and above the matrix surfaces 26, thereby serving as guides to insure alignment between the part to be formed and the matrix surfaces.

The flexible die is adapted to assume the curvature of the part to be formed and to rigidly maintain said curvature by placing the flexible die in operative engagement with a templet 22 having an edge 22:: of the curvature of the part to be formed. As a preliminary step, the die may be curved to the approximate curvature before the templet is placed in operative position. With the templet 22 set in place on top of the flexible die, the claws 21 are slidably engaged with the edge 22a of the templet, thereby properly registering each segment 24 with the edge 22:: to impart the curvature of the edge 22a to the flexible die. In order to maintain the die rigidly in this curvature, the claws 21 are anchored to the templet by bolts or screws 23 which pass through holes 21a (Fig. 2) in the claws to threadably engage the holes 22b formed in the front edge of the templet. Of course, vertically disposed screws or any other suitable means may be employed to attach the templet to the die. For greater accuracy, the faces of the hook or claw-like registering members 21 engaging the templet may be suitably fashioned to abut the portion of the edge 22a of the templet which it is adapted to contact.

As shown in Figures 1 and 3, only the end segments of articulated die are anchored to the templet by the screws 23 to prevent longitudinal displacement of the articulated die with respect to the templet. Under certain conditions of use, it may be necessary to anchor only one end of the articulated die to the templet.

In the form shown in thedrawings, the registering members 21 slidably engage with and receive the master edge of the templet, although this is not essential. The primary function of the registering members is to register the segments relative to the master edge of the templet. Therefore,,as used herein to describe the registering members, the terms hook-like and claw-like are intended to include a registering member which has a part which is secured to the die segment and an upright part which is adapted to abut the master edge of the templet.

The articulated die is a relatively heavy forming tool,

at least in comparison to the templet 22. The templet 22 may be formed from flat metal stock, such as steel or aluminum, and it is evident that the templet is a relatively inexpensive part which can be made at a fraction of the cost of a die. Different templets may be substituted to impart different curvatures to the articulated die.

The application of the present invention to stretch forming processes is represented in Fig. l of the drawings. A templet 22 having an edge 22a of the curvature which is to be imparted to the metal part A (shown in broken lines before and during the stretch forming operation) is selected, and the flexible die is mounted to the templet with the claws 21 in registered engagement with the edge 22a. The die and templet assembly is then anchored to a base F (Fig. 2) by the clamps I which are vertically movable upon the vertical guides I7. The metal part A is then grasped at both ends by chucks B which stretchpull the part against the matrix face 26 of the die. It is evident that as the ends of the part are stretched in opposite directions around the matrix face 26 of the die, the part will assume the desired curvature of the die.

Figs. 4 to 8, inclusive, illustrate the manner in 'which the present invention can be used in the formation of parts of various cross-section configurations. In Fig. 4 a U-shaped channel H is shown being forced against a flexible die with a flexible filler I, composed of individual segments flexibly together much in the same fashion as the flexible die, set into the channel to prevent the collapse or buckling of the side walls. In Fig. 5 the U-shaped part G is shown being formed with the lower surface of the base thereof in contact with the flexible die and the upstanding members disposed away from the die and accommodating a flexible filler I therebetween. Fig. 6 illustrates the reverse bending of the same U-shaped part, represented by the reference character I, the part being formed with the upper surface of the base thereof in contact with the flexible die and the die disposed between the upstanding leg members thereof. Shims 27 between the upper surfaces of the die segments 24 and the claws 21, and shims 28 beneath the segments 24 permit the front edge of the die to be received between the leg portions of the part.

Fig. 7 shows a more complex arrangement wherein upper and lower oppositely disposed dies separated by a shim 29 are employed to form apart T of T-shaped crosssection. Another shim 29 may be employed to support the lower templet above the base F to provide a space to accommodate the lower claw member 23.

Fig. 8 illustrates the use of the flexible die in forming parts E of L-shaped cross-section. In this case the templet 22 is suitably mounted above the base F, as by attaching the templet 22 to the top surfaces of blocks 80 by bolts 83 which secure both the templet and the blocks to the base F. The claw members 21 of the flexible die may then be mounted in registered position along the operative edge 22a of the templet to assume the desired contour, and a shim w placed beneath the die to accommodate the lower horizontally disposed leg of the part. The part is then formed against the lower corner of the die.

The importance of firmly anchoring the flexible die of the present invention when employed in stretch forming operations is evident, and Fig. 9 shows a mechanism preferably employed in place of the clamps shown in Figs. 1', 2 and 4 to 7, for resiliently clamping the die in operative position. The frame 36 of the clamping device is aseaaes supported above a base 31, and the frame 30 is provided with a horizontally disposed platform 32 upon which the flexible die member, generally represented by the reference numeral C is adapted to be mounted. The die C is similar to the die described in connection with Fig. 7.

The upper end of the frame 3t} supports an air cylinder 34 having a vertically movable piston attached to the shaft 35 thereof, and a vertically disposed cylindrical shaft 36 forms an extension of the piston shaft 35. The downward travel of the piston is controlled by admitting air under pressure from any suitable source via the conduit 38, and the upward travel of the piston is controlled in similar fashion via the conduit 39.

The shaft 36 is journalled in upperand lower bearings 4t 41, respectively, of the frame 36, and a clamp member 42 is jonrnalled on the shaft 36 for free sliding movement thereon. The periphery of the shaft 36, however, is serrated as at 44, and the clamp 42 has pivotally mounted at 45 thereon a hand lever 46 which controls the horizontally sliding movement of a pin 47 to move it into or out of operative locking engagement with the serrations 44 of the shaft 36.

The upward travel of the clamp member 42 is limited by the lower end of a screw 49. The threaded member 49 is threaded at its lower end through a hole 40a formed in the bearing head 40, and the vertical movement of the threaded member 49 is guided in the vicinity of its upper end by a guide plate 50. The extreme upward end of the threaded member 49 carries a crank arm 51 for rotating the threaded member 49 to move it in an axial direction upwardly or downwardly.

The lower end of the threaded member 49 is more clearly shown in Fig. 10, and it carries a square-headed bolt 52 which is threadably received in the extreme lower end of the threaded member 49. The clamp member 42 is provided with two spacially separated, vertically disposed members 42a and 42b which support a stop plate 42c above them. The stop plate 420 has an opening 42d therein to allow passage of the shank of the bolt 52, and by this means the travel of the clamp member 42 is limited in the closing direction by the head of the bolt, and in the releasing direction by the base of the threaded member 49 to facilitate removal of the part after forming.

The flexible die C is adapted to be held in place upon the platform 32 of the frame structure 30 by the clamp member 42 from above, and also by a stationary lower clamp 54 attached by bolts 55 to the platform 32.

The flexible die C is maintained in fixed position relative to the surface 31 by a plurality of the retainer units of the type just described and the units are separated at fixed intervals to obtain the anchorage needed. In setting up the retainer units for anchoring the flexible die C, the crank handles 51 are turned, lowering the clamps 42 into contact with the upper surface of the flexible die, and then the hand levers 46 are operated to move the locking members 47 into locking contact with the shafts 36. With the clamps 42 locked to the shafts 36, air is admitted into the air cylinders 34 to force the pistons and the shafts 36 downwardly to thereby place a force on the clamps 42. The set screws 52, however, prevent downward movement on the clamps; until their stop positions are lowered by the rotation of the cranks 51 in the proper directions, whereupon the clamps 42 are permitted to gradually descend under air pressure until the flexible die is resiliently but firmly anchored in place.

The flexible die C shown anchored to the base 32 in Fig. 9 actually comprises upper and lower oppositely disposed flexible dies 60 and 61, respectively, positioned relative to each other in similar fashion to the dies described in connection with Fig. 7.

In setting up the retainer units to anchor the flexible die C, the lower flexible die 61 is inverted, and the templet 22 to which it is attached is set upon a spacer plate its rear edge in position against the clamp $4. The spacer plate 70 provides clearance for the claw members of the flexible die 61. The templet of the upper flexible die 60 may be mounted to the movable clamp 42 by bolts 71,and the claws of the die 60 are placed in registered contact with the operative edge of the templet. Before applying closing pressure to the clamps 42, shims 74 having a thickness of slightly less than the leg of the T-section part D to be formed may be pinned or held in place by vertically disposed dowels 76 between the segments of the upper and lower flexible die 60 and 61. The dowels 76 will also assist in the alignment of the upper and lower flexible dies during the assembly thereof.

It should be noted thatduring the stretch bending operation to form the part D, the transverse bending load is taken up by the abutment of the rear edges of the upper and lower templets 22 against the surfaces 72 of the upper clamp member and 73 of the lower clamp member.

As mentioned above, the flexible die of the present invention can also be used in press forming operations, and the application ofthe present invention to form parts of T cross-section by press forming methods is illustrated in Figs. 11 to 15.

One of the most diflicult parts to form in conventional presses is the T-section part. Aside from the fact that a male and female die must be constructed for forming each piece having a different curvature, even though the cross-section of the members might be identical, difficulty is often experienced because of the deformation of the vertical leg of the T-section which is expected to enter a female slot or guide during the deformation thereof. Considerable care must be taken in bending a T-section using conventional male and female dies to insure that the vertical leg portion of the T-section enters the female die for support along its complete length, and the slightest warp or twist of the vertical leg will prevent it from properly entering the female die during the forming operation. This difficulty, therefore, makes it necessary, using conventional methods, to form the part in a series of steps wherein the part is initially formed until the leg begins to twist or warp, whereupon it is removed, hammered straight and replaced in the die for further forming until further warping or twisting requires this operation to be repeated. It may, of course, be necessary to repeat this correcting operation many times before the vertical leg of the T-section enters the slot of the female die sufliciently to prevent further twisting or deforming thereof.

Referring to Fig. 11, the flexible die of the present invention may be employed to overcome this difliculty since the vertical leg portion of the T-section part K may be inserted along its entire length in the flexible female die of the type shown in Fig. 12 before the bending operation. During the bending or forming operation, the female die, when brought under pressure of a com panion male die will gradually deflect to assume the contour of one of more templets with which it is operatively associated thereby gradually forming or bending the T-section member. Thus, the advantage of this method is that the entire length of the T-section part is maintained in registration with the female die throughout the forming operation, with the result there is no danger of the vertical leg portion twisting or warping during the bending operation.

Referring to Figs. ll and 13, the male die comprises a frame 90 adapted to be attached to the platen 91 of the press, a pair of downwardly depending and spacially separated templets 92 attached to the frame, and a flexible die represented by the reference numeral 93. A pair of vertically disposed side walls 94 are disposed outboard of and parallel to the templets 92, and the walls 94 are separated from the templets 92 by spacer members 99.

The construction of the flexible die 93 is generally similar to those previously described and comprises a plurality of individual segments 96 flexibly held together by a linkage 97 extending along both sides (see Fig. 11) of the segments 96. The links are connected to each other and to the segments 96 by pins 97a. Thehooks or claws 98 for engaging the curved edges of the templets are mounted on opposite sides of each of the segments 96 in order that the flexible die may be rigidly held between the two spacially separated templets 92.

The female die 100, as best shown in Figs. 11 and 12, comprises a frame 101 which is adapted to be held to the base 102 of the press, a pair of parallel side walls 103 upstanding upon the frame 101, a pair of templets 104 inboard and adjacent to the side walls 103, being spacially separated therefrom by spacer members 105, and a plurality of flexibly connected segments 106 slotted as at 107 to accommodate the vertically disposed portion of the T-section part K to be formed. The segments 106 are flexibly connected by pivot links 107 extending along both lateral sides of the segments and held thereto by pins 107a.

Thelower segments 106 also carry the templet receiving claws 109 mounted on opposite sides of the segments 106. However, unlike the hooks or templet receiving members 98 of the upper die 93, the claws 109 are not anchored to the curved edges 104a of the templets 104, but in the normal position are maintained horizontally disposed by the springs 110. The springs 110 may, of course, be replaced by ot'her equivalents, such as air or hydraulic cylinders or any other means to exert suflicient tension upon the die 100 to maintain it taut and to prevent it from sagging under normal force of gravity.

With the female die 100 maintained taut under the tension of the springs 110, the vertically disposed portion of the T-section may be readily inserted in the lengthwise slot 107 thereof along its entire length. As the platen 91 lowers, the upper male die 93 moves downwardly against the upper surface of the part K and gradually deflects both the part K and the lower die 100 against the outward supporting force of the springs. The templets 104 guide the flexible die 100 as it gradually deforms and, of course, the upper contoured edges 104a of the templets determine the limit of deformation of the lower die 100. i

As best shown in Fig. 11, the side plates 94 of the upper die and the side plates 103 of the lower die serve as guides to insure that the dies meet in proper alignment.

Figs. 14 and 15 illustrate a lower die which may be employed to form a reverse curvature in the stiffener part K of inverted T cross-section, as well as forming a joggle in each end as frequently required in such stiffeners. Ordinarily, in forming such stiffeners it is necessary to provide a separate die for forming the joggle end, however, the part may be formed in a single operation with the flexible die of the present invention. The flexible die 115 comprises individual segments 116 flexibly held together by linkages 117 connected along both. side walls of the segments 116. However, the last few end segments 116 are adjustable axially so that the claws 118 formed with keys 119 may engage suitable slots 120 formed in the edges in the templets 121. To permit axial adjustment necessary to permit the keys 119 to engage the corresponding slots 120 of the templet 121, the links 117a of the end segments are slotted as at 11711 for a limited degree of free axial movement. This limited freedom also makes it possible to employ the flexible die in conjunction with templets of different curvatures and slightly different spacing of the notches 120. Although not shown in the drawings, the upper die assembly may be of the same general construction.

The invention has been shown in a preferred form only and by way of example, and obviously many variations and modifications may be made therein without departing from the spirit of the invention. The invention is, therefore, not to be limited to any specified form or em bodiment except insofar as such limitations are set forth in the claims.

I claim:

1. Apparatus for forming parts by stretch forming methods comprising a plurality of rigid die segments, each having a forming surface and a base surface, flexible connecting means joining the segments together with adjacent segmentsvirtually contiguous to each other in a series, said flexible connecting means permitting adjacent segments to assume different angular positions relative to each other in a plane parallel to the base surfaces of the segments, a rigid, relatively flat templet having a relatively narrow master edge, a hook-like element on the portion of each segment opposite the base surface of each die segment, said hook-like members engaging the narrow master edge of the templet to register the segments rela tive to the master edge when the templet is positioned on top of the segments, thereby imparting the curvature of the master edge of the templet to the forming surfaces of the segments, and means for fixedly securing said templet and die segments in their adjusted positions on a base member.

2. Apparatus for forming parts by stretch forming methods as set forth in claim 1 including means for locking at least one of the end segments in fixed relationship with the templet.

3. Apparatus for forming parts by stretch forming methods as set forth in claim 1 in which the said element is a separate member attached to the surface of the segment opposite the base surface.

4. Apparatus for forming parts by stretch forming methods as set forth in claim 1 in which duplicate inverted assemblies are spaced apart from each other by a shim, whereby said apparatus may be used for bending a T- 8. shaped material with the part which forms the base of the T-positioned between the assemblies.

5. Apparatus for forming parts by stretch forming methods as set forth in claim. 1 in which the registering element is adapted to slidably receive the master edge of the templet.

6. Apparatus for forming parts by stretch forming methods as set forth in claim 1 in which the registering element extends forwardly of the forming surface and then upwardly, the forwardly extending portion serving as a guiding portion in bringing the part to be formed against the forming face.

References Cited in the file of this patent UNITED STATES PATENTS 1,275,377 Buckley et a1. Aug. 13,.1918 1,351,472 Farmer Aug. 31, 1920 1,520,373 Taylor Dec. 23, 1924 1,776,083 Peterson Sept. 16, 1930 1,851,884 Zerbi Mar. 29, 1932 1,961,109 Ragsdale May 29, 1934 2,142,443 Goin Jan. 3, 1939 2,192,552 -Kinney Mar. 5, 1940 2,569,266 Thompson Sept. 25, 1951 2,602,215 Moohl July 8, 1952 2,729,265 Jones Jan. 3, 1956 FOREIGN PATENTS 528,225 France Nov. 8, 1921 OTHER REFERENCES Principles of Stretch-Wrap Forming, Hufford Machine Works Inc., 1950, pages 48-49. 

